When landing poorly from a jump, your leg is likely to break at a point just above the ankle where the cross-sectional area of the bone (the tibia) is smallest. The tibia has a radius of 0.70.7cm. A bone will fracture when the compressive stress on it exceeds 130130MPa.

Your intrepid physics instructor (mass 6060kg) jumps from a desktop of height 1.21.2m onto a concrete floor, landing evenly on two legs. How much should she bend her knees to avoid breaking bones? Specifically, what is the minimum stopping distance dd such that the stress on the tibia during her landing is sufficiently low that it will not break? Give your answer in cm.

Notice that landing with stiff knees greatly decreases this stopping distance and is thus a really bad idea.

1. 6) Which options below are true? [Enter your answer as a string of the letter options you believe are correct. For instance, if you think options A, D, and E are correct, then enter "ADE"]
   
   A) Particle 2's electric field contributes to the electric force on particle 1.
   B) Particle 1's electric field does not contribute to the electric force on particle 1.
   C) If particle 2 were removed, there would no longer be a non-zero electric field at its location.
   D) If particle 2's distance from particle 1 is tripled, particle 1's electric field at 2's new location is no different than before since the field does not depend on the the properties of particle 2.
   E) None of the above

(Please note that I put this question up already and they got AC and it was wrong. This does not include that CD are wrong, there can be more right answers, one can be wrong, or both).

1. [2 marks] Describe how ultrasound waves interact with matter

A mass spectrometer is being used to separate common oxygen-16 from the much rarer oxygen-18, taken from a sample of old glacial ice. (The relative abundance of these oxygen isotopes is related to climatic temperature at the time the ice was deposited.) The ratio of the masses of these two ions is 16 to 18, the mass of oxygen-16 is 2.66 ✕ 10⁻²⁶ kg, and they are singly charged and travel at 3.70 ✕ 10⁶ m/s in a 1.70 T magnetic field. What is the separation (in m) between their paths when they hit a target after traversing a semicircle?

You are riding on a roller coaster and sitting on a bathroom scale. Where on the ride will you weight the most? Explain using a force diagram.

A 164.7g cue ball (diameter = 58.1 mm) is struck with a cue stick over a period of 0.008 s with a force of 28 N. Assume no slipping or frictional forces, the cue ball elastically hits an identical billiard ball at rest. The cue ball deflects at 60degree and the target ball at an angle of 30°. a) The speed of the cue ball after it is struck by the cue stick is ____ m/s. b) The speed of the target ball after it is deflected from rest is ____ m/s c) The kinetic energy of the cue ball after collision is ____ J. d) The kinetic energy of the target ball after collision is ____ J.

Big buildings get hit by lightning all the time. Why don’t they burn down?

Is there a relationship between thunder and lightning?

What safety procedures should be followed when dealing with lightning?

“Lightning never strikes twice in the same place”. Is this a myth or a fact?

Is there a connection between lightening formation and global warming?

(each one 100 words, total 500 words)

Plz do not copy paste anything.

Thanks

Activity 5a Gravity and Mass of the Earth Objectives: The purpose of this lab is to measure g, the acceleration of gravity at the surface of earth, and use it to calculate the mass of the Earth. Introduction: The Gravitational Constant The force felt on an object on earth is due to gravity which is defined with the relations: F_g = mg (1) Where Fg is the force due to gravity and m is the mass of the object and g is the acceleration due to gravity that is felt on the Earth's surface. The value of g depends on the mass of the Earth and the distance from the center of the Earth, as well as the universal gravitational constant, G. Thus the force felt on an object due to gravity can also be defined as: F_g=GMm/R^2 (2) Where M is the mass of the Earth, m is the mass of the object, and R is the distance to the center of the Earth to the center of the object. Activity I: Mathematical activity Put the two equations together and write g in terms of G, M, and R. Does the acceleration due to gravity, g, depend on the mass of the object being accelerated? Acceleration of a Dropped Object When an object is dropped from a height h above the surface of the earth, the amount fallen by the object is time dependent and it is given by the relation: h=1/2 gt^2 (3) The new term t in equation (3) is the time it takes for the object to drop. Equipment: A golf ball (or similarly heavy, small object); A stopwatch (can be a phone); Height of at least 4-5 meters (about 15ft); A string and ruler, or other method of measuring height Activity II: Dropping Objects With equation (3) g can be deduced if h and t are known. Thus we will measure both the height and time it takes to drop in other to deduce g. First, select a place to drop your ball, and measure the height. One method is to use a piece of string long enough to reach from the top to the bottom, and then measure the length of the string. This may be easiest with the help of a friend to hold the other end of the string or tape measurer. Make sure to use a metric measuring device (meters). If you only have a way to measure feet you will have to convert to meters (1ft = .305m) What is the height you will drop from? (in meters) We also need to characterize our measurement error/uncertainty. You should think about whether or not you stretched your string at any point, how big your ruler was compared to the string, and how finely you could measure the string compared to the ruler. With this in mind, estimate how far off your measured height could be from the actual height in meters. This is called the uncertainty in height. You can calculate the percent uncertainty by dividing the uncertainty in height by the total height measurement. What is your percent uncertainty for the height measurement? Time the Drop. Do not record the first two drops as you get used to the setup. Repeat 20 more times in order to make sure you've timed the drop of the ball well. This minimizes some of the errors that have to do with stopping and starting the stopwatch at the right time. Be careful to drop the ball from the exact height you measured, and to drop the ball rather than throw it. Tabulate your results below Drop # Time/(s) Drop # Time/(s) Drop # Time/(s) 1 8 15 2 9 16 3 10 17 4 11 18 5 12 19 6 13 20 7 14 Find the average time of all the 20 drop times in the table above. Estimate the error ∆t in the time measurements using the relations. ∆t=(t_high-t_low)/2 (4) Rearrange equation (3) and write g in terms of h and t. Use your measured values for h and t to calculate g. It is essential to note that g has been reported precisely at g = 9.8m/s2. Calculate the difference (subtraction) between the reported value of g and the value you calculated in the previous step. The difference between the two numbers (the reported constant and your calculated value) is due to errors in the measurement of h and t. In your estimation, which error had a larger effect on the result, Δh or Δt (hint: compare their percent uncertainties)? Next, we are going to use the errors in the measurement of h and t to calculate the range of possible values of g. Let’s define: t_max=t+∆t t_min=t-∆t h_max=h+∆h h_min=h-∆h Such that the upper value of g will be calculated with h_max and t_min and lower values of g will be calculated with h_min and t_max with the relations; g_max=(2h_max)/(t_min^2 ) and g_min=(2h_min)/(t_max^2 ) What are your upper and lower values for g? Is the real value of g between your calculated g_min and g_max? What does it mean if the real value of g is not within your range of possible g? Part III: Mass of the Earth For this section we will use equations (1) and (2). In order to find the mass of the earth, the universal constant G and the radius of the earth R are needed. The known values are: G=6.67×10^(-11) m^3⁄(kgs^2 ) R=6.40×10^6 m The reason we are giving you the value for R and using it to calculate M (instead of the other way around) is because R is much easier to measure than M. The radius of the Earth can be measured with a few observations and some geometry. The mass is much harder to measure directly. In the earlier section we wrote g in terms of M, R, and G. In this section you should put equation (1) and (2) together and find M in terms of g, G and R What equation did you come up with? Calculate a value for M using the g value you obtained earlier (in the part above). Use your g_min and g_max to calculate a Mmin and Mmax. Calculate the real value of M using the real value of g = 9.8m/s^2. How does it compare to your value of M (calculate the difference)? Is the real value of M between your Mmin and Mmax? Do you think this experiment is a reliable way to calculate the mass of the Earth? Explain. Part IV: Sources of Error List 3 things that made your measurement of g more uncertain. Of the three sources of error you have listed, pick one and explain what changes you could make to reduce or eliminate this error/uncertainty.

1. A property of spherical wave fronts is:

1. They interact with one another to always produce positive amplitude reinforcement.
2. They interact with one another to always produce negative amplitude cancellation.
3. They propagate radially outward from a center source in concentric circles.
4. They always travel at the speed of light.

1. What are the three primary units of measurement for various radiation exposures? What is each unit used for? (3 points)

Use this fact together with Equations (1) and (2):

(3)    a = Rα =

=

Solve for the tension T:

(4)    3.52

Substitute Equation (4) into Equation (2) and solve for a:

(5)    2

Use a = Rα and Equation (5) to solve for α:

3

MASTER IT HINTS: GETTING STARTED | I'M STUCK!

Suppose the wheel is rotated at a constant rate so that the mass has an upward speed of 4.52 m/s when it reaches a point P. At that moment, the wheel is released to rotate on its own. It starts slowing down and eventually reverses its direction due to the downward tension of the cord. What is the maximum height, h, the mass will rise above the point P?
h =

When an object is placed at the proper distance to the left of a converging lens, the image is focused on a screen 31.0 cmto the right of the lens. A diverging lens is now placed 14.2 cm to the right of the converging lens, and it is found that the screen must be moved 19.5 cm farther to the right to obtain a sharp image.

What is the focal length of the diverging lens?

......... cm

A student sits on a rotating stool holding two 3.2-kg objects. When his arms are extended horizontally, the objects are 1.0 m from the axis of rotation and he rotates with an angular speed of 0.75 rad/s. The moment of inertia of the student plus stool is 3.0 kg · m2 and is assumed to be constant. The student then pulls in the objects horizontally to 0.36 m from the rotation axis.

(a) Find the new angular speed of the student. rad/s

(b) Find the kinetic energy of the student before and after the objects are pulled in. before & after (J)

A raft is made of 18 logs lashed together. Each is 29.0 cm in diameter and has a length of 7.00 m. How many people (whole number) can the raft hold before they start getting their feet wet, assuming the average person has a mass of 72.0 kg? Do not neglect the weight of the logs. Assume the density of wood is 600 kg/m³

An electron jumps from the 4th orbit into 3rd orbit of 3Li7. Find the following (i) radii of both orbits (ii) Energies of both orbits (iii) wavelength and frequency of photon emitted as a result of this transition. Please show detailed work so I can understand how it is done.